With the backport of JDK-8193255, Path.of() calls have been introduced which were only added in JDK 11. This broke the bootstrap chain of JDK N with JDK N-1.

This is an OpenJDK 11u specific bug. Build failure looks like:

Creating support/modules_libs/java.base/jrt-fs.jar
/disk/openjdk/builds/openjdk-10-2018-04-06/bin/jar cfm /disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/modules_libs/java.base/jrt-fs.jar /disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/modules_libs/java.base/_the.jrt-fs.jar_manifest
/usr/bin/rm -f /disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/modules_libs/java.base//_the.jrt-fs.jar_contents
/usr/bin/find /disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/jrtfs_classes -type f -a \( -name FILE_NAME_THAT_DOESNT_EXIST -o -name "*.class" \) | /usr/bin/sed 's|/disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/jrtfs_classes/|-C /disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/jrtfs_classes |g' >> /disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/modules_libs/java.base//_the.jrt-fs.jar_contents
( ( /usr/bin/find /disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/jrtfs_classes/META-INF -type f 2> /dev/null || true ) | /usr/bin/sed 's|/disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/jrtfs_classes/|-C /disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/jrtfs_classes |g' >> /disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/modules_libs/java.base//_the.jrt-fs.jar_contents)
/disk/openjdk/builds/openjdk-10-2018-04-06/bin/jar uf /disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/modules_libs/java.base/jrt-fs.jar @/disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/support/modules_libs/java.base//_the.jrt-fs.jar_contents
true && true
gmake[3]: Leaving directory '/disk/openjdk/upstream-sources/openjdk-11-dev/make'
/disk/openjdk/upstream-sources/openjdk-11-dev/make/jdk/src/classes/build/tools/generatecacerts/GenerateCacerts.java:98: error: cannot find symbol
            try (InputStream fis = Files.newInputStream(Path.of(dir, entry))) {
                                                            ^
  symbol: method of(String,String)
  location: interface Path
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
1 error
gmake[3]: *** [CompileToolsJdk.gmk:49: /disk/openjdk/upstream-sources/openjdk-11-dev/build/linux-x86_64-normal-server-release/buildtools/jdk_tools_classes/_the.BUILD_TOOLS_JDK_batch] Error 1
gmake[3]: Leaving directory '/disk/openjdk/upstream-sources/openjdk-11-dev/make'
gmake[2]: *** [make/Main.gmk:89: buildtools-jdk] Error 2
gmake[2]: Leaving directory '/disk/openjdk/upstream-sources/openjdk-11-dev'

ERROR: Build failed for target 'images' in configuration 'linux-x86_64-normal-server-release' (exit code 2)